Platelet activating factor(PAF) was first identified in 1979 to be 1-O-alkyl-2-O-acetyl-sn-glycerol-3-phosphocholine by Benveniste et al. [C. R. Acad. Sci., Paris(D), 289, 1037-1040(1979)].
It was also reported that this PAF produces a variety of physiological responses such as platelet activation and antihypertension. The conjugates of nucleosides with PAF derivatives or with their analogues have been reported to exhibit diverse pharmacological activities such as anticancer, antiinflammation and antivirus activity in literatures [Journal of Medicinal Chemistry, 25, 1322(1982), Biochemical and Biophysical Research Communication, 85, 715(1978), Biochemica et Biophysica Acta, 69, 604(1980), J. Med. Chem., 28(2), 171-7(1985), Ibid., 31(9), 1793-8(1988), Ibid., 33(5), 1380-6(1990)].
Most of the antihypertensive agents, so far used in medicine have to be taken orally or by intravenous administration and the dosage has to be repeatedly administered to maintain proper plasma concentration of a drug.
However to achieve and maintain a plasma concentration of drug within the therapeutical range is not easy. If the plasma concentration of drug remains high it leads to related side effects and development of tolerance to the drug. The problem of economy of long term oral therapy also cannot be disregarded.
Development of transdermal therapeutic mode of delivery of antihypertensive agent with favorable pharmacokinetic parameters maintained for a long duration time, with improved convenience and patient compliance, and with minimal side effects has been for long considered necessary.